[Molecular mechanism underlying calcium handling in diastolic heart failure]
- PMID: 11798946
[Molecular mechanism underlying calcium handling in diastolic heart failure]
Abstract
Objective: To elucidate the molecular mechanism underlying calcium handling in diastolic heart failure (DHF) from mRNA level and protein expression, including L-type calcium channel, sarcoplasmic reticulum (SR) Ca(2+)-ATPase, phospholamban, ryanodine receptor, calsequestrin.
Methods: DHF was produced in rabbits by abdominal aortic coarctation. The mRNA amounts of these calcium-handling genes were measured by RT-PCR, while the protein levels of SR Ca(2+)-ATPase and phospholamban were analyzed by Western blot analysis.
Results: The content of calcium was significantly increased in myocardium of rabbits with DHF than in the myocardium of sham-operated rabbits. The SR Ca(2+)-ATPase activity of DHF rabbits was significantly reduced compared with that in sham-operated rabbits (21.1 micromol.mg(-1).h(-1) +/- 5.7 micromol.mg(-1).h(-1) vs 10.5 micromol.mg(-1).h(-1) +/- 2.8 micromol.mg(-1).h(-1), P < 0.01). RT-PCR analyses showed that the steady-state level of mRNA encoding the L-type calcium channel and SR Ca2+-ATPase was decreased significantly in rabbits with DHF compared with that in the sham-operated rabbits (micromol.mg(-1).h(-1)): 0.75 +/- 0.11 vs 1.20 +/- 0.33; 0.76 +/- 0.12 vs 1.24 +/- 0.38, P < 0.05). The SR Ca(2+)-ATPase mRNA level correlated negatively well with left ventricular relaxation time constant and left ventricular end-diastolic pressure (r = -0.81, -0.64, respectively, P < 0.05 approximately 0.01); the mRNA level of L-type calcium channel correlated negatively with left ventricular end-diastolic pressure (r = -0.74, P < 0.05). The mRNA level of ryanodine receptor correlated negatively with the left ventricular relaxation time constant too (r = -0.71, P < 0.05). Protein level of SR Ca(2+)-ATPase was significantly lower in rabbits with DHF than in the sham-operated rabbits (0.76 +/- 0.6 vs 1.02 +/- 0.09, P < 0.05), whereas the protein level of phospholamban was unchanged.
Conclusion: The L-type calcium channel and SR Ca(2+)-ATPase were down regulated in DHF. These changes may be a contributory factor for DHF.
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